1. Field of the Invention
This invention relates to a sense amplifier for reading out cell data of a semiconductor memory device, and relates to a semiconductor memory device with the same.
2. Description of the Related Art
In the field of mobile devices utilizing a large density of data such as still or moving image, there is increased a demand for NAND-type flash memories in accordance with increasing the uses. Especially, it has already been achieved a multi-level storage scheme, which is able to store two bits per cell, the NAND-type flash memory is recently made possible to store a large quantity of data in a small chip area.
Recently, there has already been provided such a flash memory that two memory cells are selected simultaneously as a pair, and data thereof is sensed at a high rate with a current detecting type of sense amplifier (for example, refer to Unexamined Japanese Patent Application Publication No. 2004-319007).
To achieve the read performance of the above-described flash memory, it is necessary for preparing such a sense amplifier that is able to detect a small cell current at a high rate.